Reverse Switch Activation Mechanism with Cam and Lost Motion Slot
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Solution Overview
Problem
Existing vehicles with PTO driven attachments, such as lawn tractors or riding mowers, face challenges in detecting when the vehicle is in reverse gear, leading to potential PTO operation before the vehicle starts moving in reverse, and this detection speed varies across vehicles and conditions.
Innovation Solution
A reverse switch activation mechanism featuring a control arm with a cam surface that activates a plunger to initiate the reverse switch when the reverse pedal is depressed, utilizing a lost motion slot to prevent the transmission control rod from moving until the pedal is fully engaged, ensuring the reverse switch is activated before the vehicle begins to reverse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reverse sensing switch is activated by depressing a reverse pedal connected to a hydrostatic transmission, then the PTO can be turned off when the vehicle is in reverse, but the reverse switch may not detect the vehicle is in reverse until after it starts traveling in reverse, and the detection speed varies across vehicles and operating conditions
Solution Approach 1:
The control arm with cam surface activates the reverse switch plunger in advance during the pedal depression stroke, before the transmission control rod moves the vehicle into reverse. This preliminary activation ensures the PTO is shut off before the vehicle actually begins moving in reverse, eliminating the detection delay while maintaining reliable shutdown functionality.
2Adaptability or versatility
If the reverse switch is activated at different speeds for all vehicles and operating conditions, then the system adapts to various scenarios, but this creates inconsistency in PTO shutdown timing across different vehicles
Solution Approach 1:
The control arm mechanism serves multiple functions: it activates the reverse switch at a consistent, predetermined point in the pedal stroke for all vehicles, while also accommodating different operating conditions through the mechanical cam surface geometry. This universal design ensures consistent reverse detection speed across all vehicles while maintaining adaptability to various operational scenarios.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures the reverse switch is activated before the vehicle starts reversing, preventing PTO operation until the correct gear is engaged, thereby maintaining safety and consistency across different vehicles and operating conditions.
Implementation Method 1
control arm having a cam surface that pushes a plunger to activate a reverse switch in response to depressing a reverse pedal
Implementation Method 2
transmission control rod connected to the control arm through a lost motion slot to prevent the transmission control rod moving rearwardly until the reverse pedal is depressed further
Data Source
AI summary
A reverse switch activation mechanism includes forward and reverse pedals connected to a control arm for pivoting the control arm in first and second directions. A cam surface extends from the control arm and activates a reverse switch if the reverse pedal is partially depressed. A transmission control rod is connected to the control arm through a lost motion slot and moves rearwardly if the reverse pedal is depressed further after activating the reverse switch. A control rod keeper on the control arm biases the control rod pin to a first side of the lost motion slot.